As we head into another heatwave, it becomes an interesting time to revisit the temperature extremes around the province.
CBC radio typically mentions the “current” province hotspot and coldspot during the afternoon weather forecasts.
The morning radio shows covering the same listening area will sometimes mention the weather extremes, and if you’re an astute listener you will notice that temperature extremes in the morning are often radically different than the afternoon. These differences are analyzed below.
Three separate CBC radio shows cover the province in the morning and five in the afternoon, but for simplicity sake, we will just look at the entire province as one area.
There are some other factors to consider, such as whether or not to include the lighthouse stations where no one lives permanently and/or stations that don’t report hourly. Also, some stations in the north only report hourly a few times per day, and haven’t recorded the daily highs and lows for several years now, so they have to be dropped from the list (namely Tetsa River and Muncho Lake).
To make up for the lack of coverage in the north I’ve added Atlin to the list which does not report hourly data. The lighthouse stations have also been included. The 123 usable weather stations were divided into 8 regions shown below.
While the temperatures are much warmer in the south than the north, there were some surprising findings on where the hottest locations can be found. Fort Nelson averages 3 days per year as the hottest place in BC in the afternoon (I supposed this should not be too much of a surprise given the fact that the Canadian hotspot yesterday was in the Northwest Territories). By comparison, Vancouver averages 0.5 days per year at the airport and 1.75 days downtown. Even in the hot southern interior, Penticton is not that much higher than Fort Nelson with 3.75 days per year.
Temperature extremes can be found at almost every weather station in the province. Only two weather stations (Powell River and Whistler) never recorded an extreme of any kind in the between 2015 and 2018.
Six stations recorded at least one extreme in each of the four categories (highest daily maximum, lowest daily maximum, highest daily minimum, and lowest daily minimum). Chetwynd, Cranbrook, Dawson Creek, both Fort Nelson stations, and Golden all recorded at least one day in each category. That’s 40% of the stations in the northern interior plus two in the southeast.
Keep in mind that this is just four years of data. I have not looked at other years, but I happened to notice recently that Tatlayoko Lake in the Chilcotin was the hottest place, not just in BC, but all of Canada (it did not achieve this feat in the previous four years), so clearly a longer time frame would increase the number of locations setting daily Provincial temperature extremes.
It is quite rare for the central interior to record the hottest afternoon temperature in the province. Smithers and Quesnel take most of those with one day each per year. Interestingly enough, it’s more common to find the hottest place in the province 1000 km north in Fort Nelson.
40% of hot days throughout the year are recorded in the southwestern interior, including the vast majority of summer days. The southwest interior covers the Okangan-Shuswap to the Coast-Cascade Mountains. That includes 4 of the top 5 in the graph below (Warfield is in southeastern BC).
How does this compare to the hot spots in the morning hours, you ask? Well, here are the same two graphs as above.
Because of rounding error, the Northern Interior shows 0% of days as the warmest place in the mornings, but it’s actually 1.5 days per year (0.75 days in Fort Nelson, 0.5 days in Chetwynd, and 0.25 days in Dawson Creek). The Only area where you never find the morning hotspot is the Central Interior (Cariboo, Chilcotin, Prince George, Bulkley, Nechako area).
Notice that the lighthouse stations jump up to almost 70% of days. This is because the winds off the ocean combined with higher humidity keep overnight temperature high. Many of these stations budge by a mere 4 degrees between morning and afternoon. By contrast, the central interior stations average up to 16 degrees of average daily temperature swings. The three highest swings in the province are all in the Central Interior (Puntzi Mountain, Tatlayoko Lake, and Burns Lake).
Much of the rest of the interior has high diurnal temperature variations as well, and thus are more likely to be the hot spot in the afternoon than the morning. For example, Ashcroft averages more than 38 days per year as the afternoon hot spot, but only 7 in the morning.
The morning cold spots are almost all in the interior. Fort Nelson leads the way with just under 70 per year following Burns Lake in the central interior, and Yoho National Park (the highest elevation weather station in BC) in the southeastern interior.
4 of the top 7 morning cold spots are in the central interior because of the high diurnal temperature variations (temperature change throughout the day).
43% of the time the coldest place in BC can be found in the central interior versus 42% of the time in the northern interior. This changes significantly in the afternoon were only 5% of days are coldest in the central interior.
Vancouver Island and the North & Central Coast were never the coldest places in BC in the afternoon over these four years. Princeton put the southwestern interior on the board with two readings in four years while two Whistler area stations each recorded one occurrence as the coldest spot in the province in the morning (putting the South Coast on the board).
The central interior warms up so dramatically most days that Burns Lake, Puntzi Mountain, Clinton, and Tatlayoko Lake combined only manage 6 days per year (once every two months) as the coldest place in the province in the afternoon. By contrast, one of these stations is the coldest place in BC 154 days per year. That’s once ever 2.4 days!
The odds of Revelstoke in the south of being the coldest place in BC come the afternoon is the same as Burns Lake and higher than Tatlayoko Lake!
So, combining all categories, how many times per year would the CBC be mentioning each location? Here is a list of selected places:
- 1) Fort Nelson = 146 (Northern Interior)
- 2) Yoho National Park = 89 (Southeastern Interior)
- 3) Osoyoos = 63 (Southwestern Interior)
- 4) Dease Lake = 61
- 5) Burns Lake = 58 (Central Interior)
- 6) Lytton = 56
- 7) Kindakun Rocks = 54 (Lighthouse)
- 8) Ashcroft = 45
- 31) White Rock = 18 (South Coast)
- 36) Kamloops = 12
- 41) Malahat = 9.75 (Vancouver Island)
- 49) Bella Coola = 7.75 (North & Central Coast)
- 59) Penticton = 4.75
- 62) Kelowna (UBCO) = 4.5
- 74) Cranbrook = 3
- 74) Prince George =3
- 76) Victoria (Airport) = 2.75
- 87) Williams Lake = 2.25
- 90) Merritt = 2
- 91) Nanaimo = 1.75
- 113) Kelowna (Airport) = 0.25
INTERESTING STATIONS OF NOTE
Yoho National Park (Southeastern Interior): The highest elevation station in BC that has a lot of cold afternoon temperature extremes.
Fort Nelson: Has the coldest winters in BC, recording the morning and afternoon extreme cold temperatures more than anyone else. By contrast, it never records the coldest extreme during the summer months.
Osoyoos: This south Okanagan community has the highest average daily maximum temperature for the year. Some of the other stations in the southwestern interior, namely Lytton and Ashcroft, have more extremely hot days (days above 35°C), but Osoyoos has a warmer average high throughout the year.
Osoyoos also has a lot of warm nights with the most number of “warmest mornings” throughout the year among non-lighthouse stations.
DIFFERENCES BETWEEN MORNING AND AFTERNOON
If you had a radio station (CBC or private) listing the morning and afternoon extremes, there would be some serious differences.
Over the past four years (2015-2018), the morning radio station would mention Burns Lake 230 times (as the coldest spot) while the afternoon station would only mention Burns Lake twice.
By contrast, the windswept lighthouse stations that account for 20% of the provincial weather stations recorded just a single minimum temperature in the morning (Rose Spit on Haida Gwaii on June 19, 2015) versus a four year total of 372 occurrences as the minimum maximum temperature.